So, I ordered the Smabat M1 and they just arrived - I got to say they are too light on the bass for my taste, making them pretty bright. Mids and highs seem great but the lacking bass really takes the joy out of them for me (i.e. compared to the HE-150 Pro which I really love, small and with great bass).
I will compare them to the ST-10 later but I was hoping for the bass-extension and -amount of the ST-10 in a smaller form factor with the M1 - this does not seem to be the case
Problem with the ST-10 I have is that they are slightly uncomfortable and at high volume, content with low bass distorts the mids/highs a little bit. But from a bass-perspective in general, the ST-10 have the best lower-bass extension+amount and I was hoping for this in the M1 as well..
Still waiting for a HE-150 Pro successor I guess, which could be the ST-10 in a smaller form factor and without the distortion issues I mentioned above. Sadly it's not the M1 it seems.